Advantageously, the component of the aforementioned type is designed to be used as a lower motor vehicle engine hood, commonly called “under-engine fairing”.
The purpose of such a closing component is to downwardly close off the bottom part of the engine cradle to isolate the engine from the outside. It also serves to protect the engine from any impacts, and to avoid projections of gravel, water and mud toward the engine, during operation of the vehicle. This component also prevents flows of oil or water from the engine from falling on the ground. This part serves to improve the aerodynamics of the vehicle (flat bottom) and optimize the various air intakes (scoops).
In a known manner, the structural components are generally manufactured in a single piece by injection, for example from polypropylene. A component of the aforementioned type is for example described in FR 2,853,297.
Such an assembly is robust, but can still be improved acoustically. In fact, in light of the greenhouse gas reduction constraints on vehicles, the current engine assemblies are generally more noisy than in the past, and require better soundproofing, for example using encapsulating techniques.
To offset this problem, it is known to position a sound absorbing layer on the under-engine fairing, which nevertheless has the drawback of increasing the weight of the structure, and therefore the fuel consumption of the vehicle.
Within the meaning of the present invention, a soundproofing assembly provides acoustic “insulation” when it prevents the entry of medium and high frequency acoustic waves into the soundproofed space, essentially by reflecting waves toward the noise sources or the outside of the soundproofed space.
A soundproofing assembly operates by “sound absorption” (in the medium and high frequency field) when the energy from the acoustic waves dissipates in an absorptive material.
A high-performance soundproofing assembly must work both by providing good insulation and absorption.